Make blog post titles unique

[javiereguiluz]

I'm trying to fix #1045.

We should make the slug unique because it's what we use to look for blog posts in the database. However, I can't make this work. If I define UniqueEntity on title, it works ... but if I define it on slug, it doesn't work (I can create any number of posts with the same slug). Anybody sees the error? Thanks!

[yceruto]

Yes, the slug value is generated after $form->isValid() (when the validation process is fired) in Admin\BlogController.php.

To make it work properly we can move this statement $post->setSlug(Slugger::slugify($post->getTitle())) before $form->isValid() and after $form->handleRequest($request). What do you think?

[javiereguiluz]

Yes! That must be the error.

However, if I move that line ... I see this error:

Argument 1 passed to Symfony\Component\String\Slugger\AsciiSlugger::slug() must be of the type string, null given.

If I change it like this:

        $form->handleRequest($request);

        if ($form->isSubmitted()) {
            $post->setSlug($slugger->slug($post->getTitle())->lower());
        }

        if ($form->isSubmitted() && $form->isValid()) {
            // ...
        }

Then I can again create multiple blog posts with the same slug, so the validation is not working.

[voronkovich]

@javiereguiluz, Calling isValid() method doesn't trigger validation. See https://github.com/symfony/form/blob/098f87036aeae1a1f4658d5f9f154b8cca628eb9/Form.php#L739

[yceruto]

Sorry for the confusion, @voronkovich is right, is the $form->handleRequest() who fires the validation process, so we're at the beginning again :)

[voronkovich]

@javiereguiluz, @yceruto I would suggest to use a form event listener:

->addEventListener(FormEvents::SUBMIT, function (FormEvent $event) {
    $post = $event->getData();
    $post->setSlug($this->slugger->slug($post->getTitle())->lower());
})

This also will decrease code duplicity, because we won't need to generate slug in both new and edit controllers.

[yceruto]

What about a custom validation by using the repositoryMethod option of the @UniqueEntity() annotation?

There we might have the chance to build the slug before checking that it's unique.

[yceruto]

This line $post->setSlug($this->slugger->slug($post->getTitle())->lower()); is unsafe, you'll need to check before that that the title value is not null. But yes, that's another option.

[javiereguiluz]

I liked both solutions a lot. I think they are both equally correct. However, I decided to try the form event solution proposed by @voronkovich because it felt more closely related to Symfony. A repository is a Doctrine thing, not a strictly Symfony thing and that's why I think we should use form events in this case. But I'm open to hear other opinions and change this. Thanks!

[voronkovich]

@javiereguiluz, should we add a functional test for this feature?